Field compressor stations for natural gas gathering commonly employ engines designed to operate on methane, the primary constituent of natural gas. However, such engines often are not adequately designed for the use of raw or field gas. Problems of engine wear and failure attributable to corrosion from the frequently high hydrogen sulfide content of the raw field natural gas have been increasing. As wells go ever deeper, sulfur-containing gases appear more frequently. At the same time, some gas fields which have not been produced due to the undesirable content of hydrogen sulfide now are coming into production. As fields mature which heretofore have had naturally high pressures requiring little or no compression for pipeline usage, the pressures tend to decline down to the point where field compressors are required. Thus, for many reasons, increasing numbers of compressors come in use. Unfortunately, the engine failure rate also is accelerating.
Another problem encountered with the use of field gas frequently involves relatively low octane rating of such gases, primarily attributable to the significant amounts of higher hydrocarbons such as C.sub.2 -C.sub.7 (ethane, propane, butane, pentane, hexane, etc.) in the natural gas stream. These adversely affect (lower) the octane rating of the field gas as a fuel.
Needed has been a method to process the field natural gas on the spot, providing an upgraded fuel gas in such quantities as needed for the engine, and recycling reject gas back into the pipeline. The installation preferably should be simple, capable of operating substantially unattended, and be energy-effective in not placing an added energy-consuming burden on the pumping station.